(Ariana Cubillos ~ Associated Press)
A flotilla of rescue vessels, meanwhile, led by the U.S. hospital ship Comfort, converged on Port-au-Prince harbor to help fill gaps in still-lagging global efforts to deliver water, food and medical help. Hundreds of thousands of survivors of Haiti's cataclysmic earthquake were living in makeshift tents or on blankets and plastic sheets under the tropical sun.
The strongest tremor since the Jan. 12 quake struck at 6:03 a.m., just before sunrise while many still slept. From the teeming plaza near the collapsed presidential palace to a hillside tent city, the magnitude-5.9 aftershock lasted only seconds but panicked thousands of Haitians.
"Jesus!" they cried as rubble tumbled and dust rose anew from government buildings around the plaza. Parents gathered up children and ran.
Up in the hills, where U.S. troops were helping thousands of homeless, people bolted screaming from their tents. Jajoute Ricardo, 24, came running from his house, fearing its collapse.
"Nobody will go to their house now," he said, as he sought a tent of his own. "It is chaos, for real."
A slow vibration intensified into side-to-side shaking that lasted about eight seconds -- compared to last week's far stronger initial quake that seemed to go on for 30 seconds and registered a 7.0 magnitude.
Throngs again sought out small, ramshackle "tap-tap" buses to take them away from the city. On Port-au-Prince's beaches, more than 20,000 people looked for boats to carry them down the coast, the local Signal FM radio reported.
But the desperation may be deeper outside the capital, closer to last week's quake epicenter.
"We're waiting for food, for water, for anything," Emmanuel Doris-Cherie, 32, said in Leogane, 25 miles southwest of Port-au-Prince. Homeless in Leogane lived under sheets draped across tree branches, and the damaged hospital "lacks everything," Red Cross surgeon Hassan Nasreddine said.
Hundreds of Canadian soldiers and sailors were deploying to that town and to Jacmel on the south coast to support relief efforts, and the Haitian government sent a plane and an overland team to assess needs in Petit-Goave, a seaside town 10 miles farther west from Leogane that was the epicenter of Wednesday's aftershock.
The death toll was estimated at 200,000, according to Haitian government figures relayed by the European Commission, with 80,000 buried in mass graves. The commission raised its estimate of homeless to 2 million, from 1.5 million, and said 250,000 people needed urgent aid.
Many badly injured Haitians still awaited lifesaving surgery.
"It is like working in a war situation," said Rosa Crestani of Doctors Without Borders at the Choscal Hospital. "We don't have any morphine to manage pain for our patients."
The damaged hospitals and emergency medical centers set up in Port-au-Prince needed surgeons, fuel for generators, oxygen and countless other kinds of medical supplies, aid groups said.
Dr. Evan Lyon, of the U.S.-based Partners in Health, messaged from the central University Hospital that the facility was within 24 hours of running out of key operating room supplies. Wednesday's aftershock was yet another blow: Surgical teams and patients were forced to evacuate temporarily.
Troops of the 82nd Airborne Division were providing security at the hospital. A helicopter landing pad was designated nearby for airlifting the most critical patients to the U.S. Navy hospital ship Comfort.
The great white ship, 894 feet (272 meters) long, with a medical staff of 550, was anchored in Port-au-Prince harbor and had taken aboard its first two surgical patients by helicopter late Tuesday even as it was steaming in.
It joined the aircraft carrier Carl Vinson and other U.S. warships offshore, along with the French landing craft Francis Garnier, which carried a medical team, hundreds of tents and other aid.
The Garnier offloaded pallets of bottled water and prepared meals at the city's quake-damaged port, while U.S. Army divers surveyed the soundness of the main pier, where trucks drove only on the edges because of damage down its center.
The seaborne rescue fleet will soon be reinforced by the Spanish ship Castilla, with 50 doctors and 450 troops, and by three other U.S.-based Navy vessels diverted from a scheduled Middle East mission. Canadian warships were already in Haitian waters, and an Italian aircraft carrier, the Cavour, also will join the flotilla with medical teams and engineers.
U.N. humanitarian chief John Holmes said at U.N. headquarters in New York that it's believed that 3 million people are affected, with 2 million of those needing food for at least six months.
Between the U.N. World Food Program and deliveries by the Red Cross and other private aid groups, about a half-million Haitians should have been reached with "reasonable quantities of food," he said. "That's still very far short of what's needed."
At the hillside tent camp, set up on a golf course where an 82nd Airborne unit has its base, the lines of hungry and thirsty stretched downhill and out of sight as paratroopers handed out bottled water and ready-to-eat meals as fast as helicopters brought them in.
In one sign of normalcy, women carried baskets of cauliflower, sweet potatoes and sugar cane into the city from farms in the hills. Some food and water was on sale in Port-au-Prince's markets, but prices had skyrocketed.
"We need money, man. I don't have enough to buy anything," said Ricardo, the newly homeless man who was seeking work and food, as well as a tent, at the golf course encampment.
Looking over the food lines there, 82nd Airborne Capt. John Hartsock said, "This is the first time I've seen it this orderly."
President Rene Preval stressed the relative quiet prevailing over much of Port-au-Prince. People understand, he told French radio, "it is through calmness (and) an even more organized solidarity that we're going to get out of this."
Concerns still persisted that looting and violence that flared up in pockets in recent days could spread. In downtown Port-au-Prince on Wednesday, dozens of men, women and children clambered over the rubble of a department store, hauling off clocks, lamps, towels, even women's hair extensions. Police stood nearby, not intervening.
The European Commission's report described the security situation as "deteriorating."
U.S. troops -- some 11,500 soldiers, Marines and sailors onshore and offshore as of Wednesday and expected to total 16,000 by the weekend -- were seen slowly ratcheting up control over parts of the city. Marine reinforcements were to help escort aid deliveries. One unescorted truck was seen screeching off Wednesday when a crowd grew unruly as its tents were being distributed.
The U.N. was adding 2,000 peacekeepers to the 7,000 already in Haiti, and 1,500 more police to the 2,100-member international force. That plan suffered a setback when Haiti -- with historically tense relations with the neighboring Dominican Republic -- rejected a Dominican offer of an 800-strong battalion, according to a Western diplomat at the U.N., speaking on condition of anonymity in the absence of a public announcement.
Other small signs of normalcy rippled over Port-au-Prince: Street vendors had found flowers to sell to those wishing to honor their dead. One or two money transfer agencies reopened to receive wired money from Haitians abroad. Officials said banks would open later this week.
But Wednesday's aftershock, the stench of the lingering dead, and the tears and upstretched hands of helpless Haitians made clear that the country's tragedy will continue for months and years as this poor land counts and remembers its losses.
After the tremor's dust settled Wednesday, street merchant Marie-Jose Decosse walked past the partly collapsed St. Francois de Salles Hospital in Carrefour Feuille, one of the worst-hit sections of town. She raised her arms to the sky, and spoke for millions.
"Lord have mercy, for we are sinners!" she shouted. "Please have mercy on Haiti."
Associated Press writers contributing to this report included Alfred de Montesquiou, Tamara Lush, Kevin Maurer, Michelle Faul and Bill Gorman in Haiti; Edith M. Lederer at the United Nations; Emma Vandore and Elaine Ganley in Paris, and Aoife White in Brussels.